Sunnyslope48

I changed my spark plugs. Not the most fun I've ever had working on a car but much cheaper than any other way of getting the job done done. Most difficult part was removing the electrical connectors from the coil packs. After having problems with the 1st two cylinders, I decided just to leave the connector attached to the coil pack and move it out of the way. That worked much, much better

I did have one problem of note and that is on #2, I must have not gotten the wiring connector pushed on all the way on the coil and that resulted in a misfire, naturally, and Blue Driver marked it as an active code. I fixed the loose connection and re-scanned, but the scan tool says that the code (P0302) is now a permanent code and the car will erase the code once the issue is resolved. I have seen many other codes (on Chevy Diesel trucks - not Mercedes) referring to having X number of successful restarts without encountering the problem and the code will go away. So my question is, when will this code be cleared by the car? Is it based on restarts without a misfire? Number of miles driven? What is the code clearing criteria that the car is looking for?

One thing I don't like about having a check engine light showing on the dash for this permanent code is that I have no way of knowing if there may be another even more serious malfunction that is masked because of the 'permanent code' that I believe the engine will clear by itself.

KEY08

Plus if you have to pass emissions tests like we do it is an immediate fail.

Sunnyslope48

I have driven the car for a few days now and it is absolutely silky smooth at idle, while driving, and the only clue about any misfire is that the CEL light is on. Usually, misfires are pretty noticeable. It certainly is possible that the misfire is very limited, but this sure is different than any other in my experience. Any ideas out there?

Darel

Not 100% about the MBs, but most cars will clear a "minor" code after 3 restarts. Something like a misfire code SHOULD (emphasis on the uncertainty of the word SHOULD) clear when you clear the codes, as well as when the issue no longer exists, at least after a couple restarts.

I recommend swapping the plug and coil to a different cylinder and seeing if the misfire moves - i.e. swap plug and coil with #5 and see if it turns into P0305. If it stays, then you either damaged the electrical connector in that spot, or something is up with the injector just out of sheer coincidence. If it moves to the new cylinder, replace the plug and coil pack. I can't count how many rabbit holes I've gone down because of new parts that were bad out of the box, and it just never occurred to me as a possibility.

Sunnyslope48

In addition to the P0302 misfire code, I also have a P0352 code, Ignition coil 'B' primary control circuit/open. So I thought that perhaps replacing the coil pack would solve the problem, but no change, still P0302 and P0352. So as I understand the P0352 code, there is an open circuit somewhere. But where.? I believe it is between the ECM and the coil. There are 4 wires into the coil, connector and coil pins look perfect and connector fits tightly. So must be further up the line.

But I am absolutely frustrated in my attempts to find wiring diagrams for my car in particular, and Mercedes in general after about 2010. Does anyone have access to wiring diagrams for this problem that they'd be willing to share?